Evenings are drawing in, lockdown 2.0 is in full swing, and most office-based companies are messaging there won’t be a return to work until at least March 2021. Watching the sunset from 4pm with one to two hours of work to go, and an evening planned beyond, is a draining experience that usually lasts the whole of Winter.
Here I’ll make the case for kitting out your workspace with sufficient lighting to stave-off some of the winter lethargy. I’ll summarise the research I’ve done and hope to save others the time and money that I spent getting to what I feel is a good solution!
Some feedback has been provided that I haven’t had time to incorporate fully.
Colour Rendering Index
The “CRI” is a measure of how close your light source represents the colours of your surroundings that you’d observe under daylight. It’s another dimension in addition to brightness and colour temperature that I didn’t mention below.
A poor CRI (<80) can leave the room feeling surreal and ugly, so you should aim to buy bulbs with CRIs >= 80 (/100, daylight).
I have since bought further into the argument that a super-bright “Seasonal Affective Disorder” lamp. It’d be wrong to claim the science is proven, but I can’t see many drawbacks whereas the benefits seem to suggest really getting those winter blues under control. I found this lecture informative, to really get over the line on changing my mind. I an relatively convinced that I am not encountering light bright enough, during the winter months, to keep my circadean rhythm in-check. If that turns out not to be super important (which I presently find unlikely), I think the additional light is not likely to have any significant downsides except for the cost.
Brightness: how much light do I need?
A quick search finds some useful calculators and recommendations putting offices with computers in the range of 20-50 lumens / square foot, where I judged the most common recommendation from a few sources to be 40. So in a 10×10 square foot room, around 4000 lumens is recommended for working.
Offices and “task” areas should be lit in the range of 20-50 lumens / square foot. I am currently finding a bulb that provides 20lm/sq ft sufficient, plus daylight.
Lumen (lm) is a general form of measurement for “amount of light”, which most bulb manufacturers will supply. Fun and useless history fact: 1 lumen is the amount of light a ‘standard candle’ (or candela) emits over a specific mathsy angular fraction of a sphere around it. Luminous flux, or Lux, is simply lumen / square metre.
The more familiar Watts (W) measure power drawn so are less useful for figuring out how much light you need versus how big your energy bill will be; that’s because filaments (that use heat as their light source) require many more Watts/lumen than LEDs (which directly convert electricity to light), for example.
Sunlight and windows
The sun can do some of the work, when it’s out. At its brightest in winter, a south-facing window in the UK can let in 5000Lux, so a 1 metre-squared window would let more than enough light in. However that can drop to 500Lux in deep shade (and ~0 when the sun sets early!). I find with a 1500lm bulb and daylight, things are bright enough, and when the sun is setting I don’t notice a huge difference. Still, I’m almost sure more would be better.
Colour: what kind of light do I need?
I was partly inspired to look into all this by Neel Nanda’s blog post on tackling winter blues of various extremities. This got me into the idea of simulating daylight to tackle my mild form of the blues, gaining more energy for the day and staving-off lethargy this time of year always brings.
I discovered that industry distinguishes colour-temperatures, which you’ll see measured in Kelvin (= degrees Celsius + 273). That is, the colour of a solid burning at that temperature. The most common temperatures available are:
- ‘Cool white’, 5700K (sometimes 5500K or 6000K), achieved with a colour-balance of different LEDs
- ‘Warm white’ at 2700K, which is the traditional temperature of tungsten filament lightbulbs, but can now be achieved with more energy-efficient LEDs
Daylight’s colour-temperature is around 5000K in the UK. I was reassured that, unlike usual black-body radiation (sorry, as a physicist I had to include the link), light bulb manufactures kindly don’t include eye-and-skin-damaging UV rays in their makeup. Looking to simulate the energy daylight usually gives me, that’s the value I’m roughly looking for to work by.
Productivity vs. sleep
Any responsible blogger should add: with great luminous power comes great responsibility. White light is white because it’s a balance of the usual red/orange plus blue light. As a numbers person, I find research on direct-correlation of sleep and blue light to be low in sample-size, at the moment (~30 people). However most signs (and theory on melatonin production) certainly point in the direction that blue light makes our monkey-brains think of daylight more than any other type of light. On the one hand that does make ‘cool white’ better for productivity, but conversely seems to affect our quality of sleep when consumed in the evening.
Industry distinguishes colour-temperatures of ‘cool white’, 5700K, and ‘warm white’, 2700K. Daylight is ~5000K, and is best for productivity, but harms sleep.
So if you’re like me and are currently working and sleeping in the same room, colour-control will be very important. Consider this if you sometimes spend evening in your office room, too.
Additionally, some say that colour-coding their environment helps them to separate work-time from evening-time, another essential balance to strike during working from home at any time of year.
Blue light is the most energetic form of visible light. It is one rung on the spectrum away from ultraviolet light, which is known to cause skin and retinal damage. In my opinion, it’s prudent to ask about the question of safety, when it comes to considering exposing ourselves to newly-invented white artificial lighting for up to 16 hours a day, every day.
Many are reassuringly quick to dismiss concerns that blue LEDs may be damaging to our retinas. However, that largely seems to be on the basis of a lack of experimental results that they do (or don’t, as far as I can see), and the difference in indoor vs outdoor light intensity.
Earlier I recommended intensities of 500lux for office spaces, which comes without UV rays. On the other hand, non-direct summer-daylight is 10,000-25,000lux, including proven-to-be-damaging UV rays. So there’s more than a 10x difference between your indoor environment’s light intensity and going outdoors in the summer. Looking at the brightest screens close-up is also 10x less intense than being out in daylight, according to a Harvard Health blog, so they say any additional risk from screens and LED bulbs is negligible to other eye-health risks we should be worrying about.
However I have seen no treatment of the fact that my pupils will be dilated when indoors in a well-lit room such that it looks as bright as the outside world. I can only imagine that’s because a similar amount of light hits my retinas. Some experts are acknowledging that “evidence of phototoxic effects of LED displays are lacking but they cannot be ruled out”. I find this to be much more credible given the aforementioned lack of evidence either way, and lack of treatment of this seemingly key observation (which admittedly may be due to a lack of my own understanding).
We do not yet know if there will be any long-term effects of overexposure to blue light, but they seem to be negligible compared to other risks to eye health
Nonetheless, nobody is saying that reflected daylight is safe for the eyes without protection, so probably best to a) not look at any bright LED lightbulbs directly and, since you’re still reading about safety, b) wear UV-filtering sunglasses outdoors (oops).
What do I buy?
I tried a cheap ‘cool white’ (6000K) lightbulb and found the blue, artificial tinge nauseating (Edit: it likely had a poor Colour Rendering Index, on reflection, which isn’t something I checked). I’m putting this down to the extremely high, fixed 6000K value, and not having enough brightness at 800lm for my ~75sq foot room. The result was a strange under-bright blue/white. Nonetheless, on switching back to my incandescent (2700K), I noticed how orange and under-lit everything is compared to my computer.
Not wanting to bite the bullet on another failed lightbulb, I took to the charts to conclude my ideal colour-temperature was around 4500K. However as I work and sleep in the same room, this is far too blue for a room that will be used in the evening as well.
As ever, technology has the answer. I always thought smart bulbs were a gimmick, but they turned out to be perfectly useful for my use-case. Computers are now so small that you can control the exact RGB value you want in every room via an Android/Apple app, over your home WiFi, with limited setup. Welcome to the Internet of Things.
Smart lightbulbs can select between a range of colour temperatures (2700K-6000K) and brightness settings. That helps achieve the perfect work-sleep schedule, when needed
I bought a single 1500lm smart bulb that has 2700K-5700K colour-temperature range. It has full brightness / colour control. I find this to be perfectly sufficient for my ~75 square foot room with dull carpets, high-ceilings and light-coloured walls, without the need for lamps – despite earlier recommendations being about double that. I have felt more energised in evenings as a result of not being so painfully aware of the sun setting at 4pm.
Alternatives to smart bulbs that can do everything for those wanting to de-tech would be a combination of cool and warm white lamps and ceiling lights. I found a single, 1500lm to be bright enough for my medium-sized office-bedroom and can have it as low as 30-50% brightness by the end of the day. So perhaps a 700lm central bulb with a similar-brightness ‘cool-white’ lamp would be one combination to look this could be something to aim for with a central-light, or something brighter in the centre with a warm white lamp to switch to in the evening.
As was buried in the text above…